Investigation of HTS Current Leads Under Pulsed Operation for JT-60SA

The test of two Wendelstein 7-X (W7-X) prototype high temperature superconductor (HTS) current leads (CL) was extended to dynamic operation, in order to evaluate AC losses in parts of the CL. Trapezoidal and triangular current cycles up to a maximum current of 20 kA with different ramp rates between 0.5 kA/s and 10 kA/s were performed. Temperature changes at the warm end of the HTS-module and the influence on the heat load at the cold end of the CL were studied. Additionally, a DC operation that generates a power loss equivalent to the triangular pulsing run was investigated. AC losses in the low temperature part of the CL are estimated by simplified models and compared to the experimental results of the heat load measurements. The effect of the AC losses on the CL performance is discussed.